Chk eng light is on again. This year its the exh manifold/cat. Whats going on?

What is your question?

Ive had my car since may 02. I did all the computer recalls..even took care of the transmision slipping problem. Thank goodness i didnt have to comeup with the cash for that job. Anyhow..my chk eng light is always on..its been on since 02 pretty much. Last time for my inspection it was o2 sensors.. before that fuel sensors... This time it is the exh manifold/cat. I get it..my car is old..fragile..whatever. but what the heck with the light always on? It wont pass inspections..its making me crazy.